The Pressure option in the Support menu, allows the user to specify a distributed force which is applied to the slope face and / or the upper face of the wedge. The pressure is specified in terms of force per unit area, and may represent:
support pressure (for example, rock bolts applied to the slope face of the wedge)
loading pressure (for example, a distributed surcharge load on the upper face of the wedge)
The Pressure option is the easiest way to model the effect of pattern bolting, or distributed surcharge loads, because the user does not have to calculate the total force, or define individual bolts (as with the Add Bolt or External Force options). When Pressure is applied, the total force applied to the wedge is automatically calculated by Swedge, based on the wedge face area(s) and the pressure magnitude.
To use the Pressure option:
Select Pressure from the Support menu.
In the Pressure dialog, use the checkboxes to select which face of the wedge you would like to apply the pressure to (the Slope Face or the Upper Face of the wedge, or both).
By default, the orientation (Trend and Plunge) of the pressure will be NORMAL to the face of the wedge (i.e. the Slope Face or the Upper Face). However, you may enter any orientation, by entering the desired Trend and Plunge. For example, if you are modeling a horizontal rock bolt pattern applied to the Slope Face, you would enter Plunge = 0).
Enter a value for the Pressure (i.e. force per unit area of wedge face).
EXAMPLE: if rock bolts with an individual capacity = 20 tonnes, are installed on the Slope Face, at a 2 meter by 2 meter spacing, then the equivalent support Pressure would equal 20 / (2 * 2) = 5 tonnes per square meter. This would be the support Pressure you would enter in the Pressure dialog.
Select either Active or Passive support model (for details about Active and Passive support in Swedge, see the topic How Bolts are Implemented in Swedge.
You can select the Apply button, to run the analysis without closing the dialog. Or select OK to run the analysis and close the dialog. You should see a change in the Safety Factor.
NOTE: when you have defined a Pressure for an Swedge model, the colour of the wedge face on which the pressure is applied, will be lightened, to indicate that pressure is applied. Also, an arrow (same colour as the original wedge colour), will appear on the wedge face, indicating the direction of the applied pressure.